“Who cares just as long as it drops,” he said.

Both men run repair shops out of their businesses. With gasoline profit margins at between 4 and 9 cents a gallon, they say it’s the repair shops that keep them in business.

“Gas is just a calling card,” Mike said. “You don’t make any money on it.”

Amid complaints against the so-called interchange fee -- a percentage of the sale price paid to credit card companies on each transaction -- a growing number of operators are suspending credit card sales.

It’s a two-edged sword, Campbell said.

“There’s so many people who can’t carry around $100 to fill up their tank,” he said.

Mike Daley, 26 of Wilmerding has used a credit card to take some of the sting out of $4 gallons of gas. The sales rep for a security agency said he hopes cash-only pumps don’t catch on.

“I’ll go somewhere else,” Daley said. “You gotta do what you gotta do.”

The cash-only push comes as Congress considers legislation that would allow merchants to bargain collectively with major credit and debit card companies.

The proposed Credit Card Fair Fee Act has the support of the Pennsylvania Food Merchants Association and the National Association of Convenience Stores.

Jeff Lenard, spokesman for the Alexandria, Va.-based National Association of Convenience Stores, called the card bans “a last resort that demonstrates how desperate retailers are to get change.”

Convenience stores paid $7.6 billion in credit card fees last year, while making $3.4 billion profits, the group said.

Although the percentage of the interchange fee is fixed, usually under 2 percent, the dollar amount of the fee goes up with the price of the goods or services. As gas tops $4 a gallon, that pushes fees toward 10 cents a gallon. Stations that typically mark up gas by 11 or 12 cents a gallon are seeing profits shrink or even reverse.

Fink said he buys gas from the distributor for $3.97 a gallon. He sells it for $4.05, but when someone uses plastic, Fink has to pay the credit card company up to 13 cents a gallon, nearly double his potential profit.

The average retailer last year made 1.5 cents per gallon on the 4,000 gallons sold a day, earning $60, Lenard said.